News tagged with time

(Phys.org)—Light behaves both as a particle and as a wave. Since the days of Einstein, scientists have been trying to directly observe both of these aspects of light at the same time. Now, scientists at ...

We've come a long way in 13.8 billion years; but despite our impressively extensive understanding of the Universe, there are still a few strings left untied. For one, there is the oft-cited disconnect between ...

On a recent trip to Australia, the National Physical Laboratory (NPL) visited one of the two sites of the Square Kilometre Array (SKA) - a global science and engineering project to build the worlds largest ...

A state-of-the-art optical atomic clock, collaboratively developed by scientists from the University of Warsaw, Jagiellonian University, and Nicolaus Copernicus University, is now "ticking away" at the National ...

When electronic states in materials are excited during dynamic processes, interesting phenomena such as electrical charge transfer can take place on quadrillionth-of-a-second, or femtosecond, timescales. ...

A new economy is taking shape – one in which sensors unblinkingly monitor the health of machines, and machines, production lines and entire factories trade logistical information in real time. Largely invisible ...

Imagine a version of Google Street View where you could hit the rewind button and see any point in time over the last five years. Cornell researchers are building something like that, at least for a few much-visited ...

Research by the University of Twente has shown that many road users do not choose the shortest or fastest route. In some situations, this applies to no less than 75% of road users. There are several reasons ...

Hillary Rodham Clinton used a personal email account during her time as secretary of state, rather than a government-issued email address, potentially hampering efforts to archive official government documents ...

The cute cat video seems to be everywhere online, and it's become a handy epithet for everything that journalism should not be. So what should we make of the fact that The New York Times, that paragon of jou ...

Time

Time is a component of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects. Time has been a major subject of religion, philosophy, and science, but defining it in a non-controversial manner applicable to all fields of study has consistently eluded the greatest scholars.

In physics as well as in other sciences, time is considered one of the few fundamental quantities. Time is used to define other quantities – such as velocity – and defining time in terms of such quantities would result in circularity of definition. An operational definition of time, wherein one says that observing a certain number of repetitions of one or another standard cyclical event (such as the passage of a free-swinging pendulum) constitutes one standard unit such as the second, is highly useful in the conduct of both advanced experiments and everyday affairs of life. The operational definition leaves aside the question whether there is something called time, apart from the counting activity just mentioned, that flows and that can be measured. Investigations of a single continuum called spacetime brings the nature of time into association with related questions into the nature of space, questions that have their roots in the works of early students of natural philosophy.

Among prominent philosophers, there are two distinct viewpoints on time. One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence. Time travel, in this view, becomes a possibility as other "times" persist like frames of a film strip, spread out across the time line. Sir Isaac Newton subscribed to this realist view, and hence it is sometimes referred to as Newtonian time. The opposing view is that time does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instead part of a fundamental intellectual structure (together with space and number) within which humans sequence and compare events. This second view, in the tradition of Gottfried Leibniz and Immanuel Kant, holds that time is neither an event nor a thing, and thus is not itself measurable nor can it be travelled.

Temporal measurement has occupied scientists and technologists, and was a prime motivation in navigation and astronomy. Periodic events and periodic motion have long served as standards for units of time. Examples include the apparent motion of the sun across the sky, the phases of the moon, the swing of a pendulum, and the beat of a heart. Currently, the international unit of time, the second, is defined in terms of radiation emitted by caesium atoms (see below). Time is also of significant social importance, having economic value ("time is money") as well as personal value, due to an awareness of the limited time in each day and in human life spans.